Claude Fable 5.1 vs GPT-5.6 Terra
Pricing, context window and real answers (September 2026)
Claude Fable 5.1 (Anthropic) and GPT-5.6 Terra (OpenAI), compared as you can actually call them on FastMetal. Both are served from the same OpenAI-compatible endpoint and API key; switching is a change to the model string.
Specs and pricing
 Claude Fable 5.1 |  GPT-5.6 Terra | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Input (per 1M tokens) | ¥1,787 | ¥357.4 |
| Output (per 1M tokens) | ¥8,935 | ¥2,144.4 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥6,255 | ¥1,430 |
| Context window | 1,000,000 tokens | 1,050,000 tokens |
| Release date | 9/1/2026 | 7/9/2026 |
| Input modalities | text, image, file | file, image, text |
| Arena · overall | #3 · ELO 1,504 | #43 · ELO 1,466 |
| Arena · Japanese | Unranked | #18 · ELO 1,474 |
| Arena · coding | #34 · ELO 1,517 | #31 · ELO 1,519 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, GPT-5.6 Terra: ¥2,144.4 per 1M output tokens, 76% less than Claude Fable 5.1.
- On the Overall arena board, Claude Fable 5.1 ranks higher (#3; GPT-5.6 Terra is #43).
- On the Coding arena board, GPT-5.6 Terra ranks higher (#31; Claude Fable 5.1 is #34).
- For long documents, GPT-5.6 Terra: a 1,050,000-token context window against 1,000,000 for Claude Fable 5.1.
- If in doubt, try both on the same key. Switching is a change to the model string, and each is billed at its own rate.
Real answers to the same prompts
Exactly what the FastMetal gateway returned, side by side. Not benchmark scores: actual output.
Count the number of 'r's in 'strawberry'
Count the number of 'r's in 'strawberry'. Explain your reasoning step by step.
Claude Fable 5.1
**Step 1: Write out the word letter by letter.**
s - t - r - a - w - b - e - r - r - y
**Step 2: Number each position.**
1. s
2. t
3. **r**
4. a
5. w
6. b
7. e
8. **r**
9. **r**
10. y
**Step 3: Identify which positions contain 'r'.**
- Position 3: r (in "str-")
- Position 8: r (in "-ber-")
- Position 9: r (in "-rry")
**Step 4: Count them.**
3 + 1 + 1 = **3**
**Answer: There are 3 'r's in "strawberry."**
A helpful way to check: split the word into its parts — "straw" (1 r) + "berry" (2 r's) = 3 r's total.
7.9s259 output tokens
GPT-5.6 Terra
“strawberry” is spelled:
s t **r** a w b e **r** **r** y
There are **3** occurrences of the letter **r**.
3.6s71 output tokens
Debug This Error
I'm getting the following error in my Node.js application: TypeError: Cannot read properties of undefined (reading 'map') at UserList (/app/components/UserList.js:12:25) at renderWithHooks (/app/node_modules/rea…
Claude Fable 5.1
The error means that when `UserList` rendered, the `users` prop was `undefined`, so calling `.map()` on it failed. This typically happens because:
1. **The parent isn't passing the prop** (or misspelled it, e.g. `<UserList user={...} />`), or
2. **The data hasn't loaded yet.** A common pattern is fetching users in a `useEffect` and storing them in state whose initial value is `undefined` (e.g. `useState()`), so the first render happens before the data arrives.
**Fixes**
Give the prop a default value so the component is safe to render with no data:
```jsx
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}…
10.8s564 output tokens
GPT-5.6 Terra
The error means `users` is `undefined` when `UserList` renders, so React tries to evaluate:
```js
users.map(...)
```
But `.map()` only exists on arrays.
Common causes:
- The parent component does not pass a `users` prop.
- The user data is loaded asynchronously and has not arrived on the first render.
- The API response shape differs from what you expect, e.g. data is in `response.data.users` rather than `response.data`.
- The parent initializes its user state as `undefined` or `null`.
## Fix options
### 1. Initialize users as an empty array
In the parent component:
```jsx
const [users, setUsers] = useState([]);
```
Then pass it normally:
```jsx
<UserList users={users} />
```
An e…
5.8s559 output tokens
Code Review
Please review the following Python function and suggest improvements for readability, performance, and best practices: def get_data(url, retries=3): import requests import time for i in range(retries):…
Claude Fable 5.1
Here's a review of the function organized by category, followed by a refactored version.
## Issues
### Correctness / robustness
1. **Bare `except:`** — This catches *everything*, including `KeyboardInterrupt`, `SystemExit`, and bugs like `KeyError` from `item["active"]`. A malformed response would be silently retried three times and then swallowed. Catch `requests.RequestException` (and `ValueError` for bad JSON) specifically.
2. **Retrying non-retryable errors** — A 404 or 400 will never succeed on retry. Only retry on transient failures (timeouts, connection errors, 5xx, 429).
3. **Silent failure** — Returning `[]` after exhausting retries is indistinguishable from "the endpoint legitima…
27.7s2028 output tokens
GPT-5.6 Terra
Here are the main areas to improve:
### Issues in the original code
- **Imports inside the function**: Move `requests` and `time` imports to module scope.
- **Bare `except:`**: This catches everything, including `KeyboardInterrupt` and programming errors. Catch `requests.RequestException` (and possibly JSON decoding errors) instead.
- **Status code check**: Prefer `response.raise_for_status()` or `response.ok` over manually checking only for `200`. Successful responses can include other 2xx status codes.
- **`== True`**: Use `if item.get("active"):` instead.
- **Potential `KeyError`**: `item["name"]`, `item["id"]`, and `item["active"]` can fail if the API response is incomplete. Use `.get(…
10.6s939 output tokens
Frequently asked questions
- Which is cheaper, Claude Fable 5.1 or GPT-5.6 Terra?
- Per 1M output tokens, Claude Fable 5.1 is ¥8,935 and GPT-5.6 Terra is ¥2,144.4 on FastMetal (yen, before tax), so GPT-5.6 Terra is cheaper.
- How do the context windows of Claude Fable 5.1 and GPT-5.6 Terra compare?
- Claude Fable 5.1 takes 1,000,000 tokens; GPT-5.6 Terra takes 1,050,000.
- Which ranks higher, Claude Fable 5.1 or GPT-5.6 Terra?
- Claude Fable 5.1 ranks higher on the public arena (Claude Fable 5.1 #3, GPT-5.6 Terra #18). Ranks move as the leaderboard updates.
- Can I use Claude Fable 5.1 and GPT-5.6 Terra with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-fable-5-1" or "gpt-5.6-terra" as the model. Each is billed at its own rate from the same prepaid balance.
Try both on one API key
Create an account and add credit to call Claude Fable 5.1 and GPT-5.6 Terra from the browser chat and the API. No monthly fee.